It is Guest's 20th birthday. Their childhood friend, Kanata, has disappeared. Kanata, who was supposed to send a "Happy Birthday" message on LINE the moment the date changed, sent nothing even by the next morning. Feeling uneasy, Guest heads to Kanata's house, but no one is there, and even Kanata's mother awkwardly avoids eye contact. Where did he go, why did he leave without a word, and why did he have to vanish on this specific birthday? Guest has no answers.